WO2018066905A1 - Method and device for performing v2x communication - Google Patents

Abstract

Provided are a method by which a base station performs vehicle to everything (V2X) communication in a wireless communication system, and an apparatus for supporting the same. The method can comprise the steps of: receiving a V2X bearer indication indicating a V2X bearer, wherein the V2X bearer is a bearer used for a V2X service; determining that the base station supports only a PC5-based V2X service between the PC5-based V2X service or a Uu-based V2X service; postponing a resource allocation for the V2X bearer; and transmitting, to a mobility management entity (MME), information indicating that the resource allocation for the V2X bearer is postponed.

Description

Method and apparatus for performing V2X communication

The present invention relates to a wireless communication system, and more particularly, to a method for holding resource allocation for a vehicle to everything (V2X) bearer and a device supporting the same.

Recently, interest in D2D (Device-to-Device) technology for direct communication between devices is increasing. In particular, D2D is drawing attention as a communication technology for a public safety network. Commercial communication networks are rapidly changing to LTE, but current public safety networks are mainly based on 2G technology in terms of cost and conflict with existing communication standards. This gap in technology and the need for improved services have led to efforts to improve public safety networks.

Public safety networks have higher service requirements (reliability and security) than commercial communication networks, and require direct signal transmission and reception, or D2D operation, between devices, especially when cellular coverage is not available or available. .

D2D operation may have various advantages in that it transmits and receives signals between adjacent devices. For example, the D2D user equipment has a high data rate and low delay and can perform data communication. In addition, the D2D operation may distribute traffic congested at the base station, and may also serve to extend the coverage of the base station if the D2D terminal serves as a relay.

V2X (vehicle to everything) is a technology that adds mobility to D2D technology, allowing vehicles to continue to communicate with road infrastructure and other vehicles as they drive, exchanging and sharing useful information such as traffic conditions.

Efforts have been made to develop an improved 5th-generation (5G) communication system or a pre-5G communication system to meet the increasing demand for wireless data traffic since the commercialization of a 4th-generation (4G) communication system. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (beyond 4G network) or after a long term evolution (LTE) system (post LTE).

On the other hand, when the base station has set the configuration for the V2X transmission to 'PC5 only', the terminal receiving the 'PC5 only' setting can be seen that the V2X message can not be transmitted through the Uu interface. Also, the base station may not transmit the V2X message using the V2X bearer. In this situation, since no traffic is carried over the V2X bearer, it is not a problem that the V2X bearer is not released. Since the V2X bearer can always be used while the terminal is located in the network supporting the V2X service, while the terminal is located in the network supporting the V2X service, the V2X bearer does not need to be released. This is because releasing the V2X bearer may cause signaling overhead. Therefore, the base station set to 'PC5 only' needs to withhold resource allocation for the V2X bearer. In addition, the terminal located in the base station set to 'PC5 only' needs to maintain the context of the V2X bearer without deactivation.

In one embodiment, a method for a base station to perform a vehicle to everything (V2X) communication in a wireless communication system is provided. The method includes receiving a V2X bearer indication indicating a V2X bearer, wherein the V2X bearer is a bearer used for a V2X service; Determining that the base station supports only the PC5 based V2X service among the PC5 based V2X service or the Uu based V2X service; Withholding resource allocation for the V2X bearer; And transmitting information indicating that resource allocation for the V2X bearer is suspended to a mobility management entity (MME).

If the base station is determined to support only the PC5 based V2X service, resource allocation for the V2X bearer may be suspended.

The method may further include transmitting information indicating that resource allocation to the V2X bearer is suspended to the terminal. The base station is a target base station, the information transmitted to the terminal may be transmitted to the terminal via a source base station. The information may include an identifier (ID) of the V2X bearer.

The method includes determining that the base station supports the Uu based V2X service; And allocating resources to the V2X bearer. The method includes establishing a DRB for the V2X service based on resources allocated for the V2X bearer; And transmitting information indicating that the DRB for the V2X bearer is established to the MME.

In another embodiment, a method of performing a vehicle to everything (V2X) communication in a wireless communication system is provided. The method includes receiving information from a base station indicating that resource allocation for a V2X bearer is suspended, wherein the V2X bearer is a bearer used for a V2X service; Performing marking on the V2X bearer instructing to suspend deactivation of the V2X bearer; And maintaining a context of the marked V2X bearer.

If the base station supports only the PC5-based V2X service among the PC5-based V2X service or the Uu-based V2X service, resource allocation for the V2X bearer may be suspended by the base station.

The device may be a mobility management entity (MME). If the device is an MME, the method includes receiving information from the base station indicating that a DRB for the V2X bearer has been established; And if the information indicating that the DRB has been established is removed, removing the marking from the V2X bearer.

The device may be a terminal. If the device is a terminal, the method includes receiving an RRC connection reconfiguration message from the base station; And if the RRC connection reconfiguration message is received, removing the marking on the V2X bearer. The AS layer of the terminal may inform the NAS of the terminal that the DRB for the V2X bearer is established.

In another embodiment, a base station for performing vehicle to everything (V2X) communication in a wireless communication system is provided. The base station includes a memory; Transceiver; And a processor connecting the memory and the transceiver, wherein the processor controls the transceiver to receive a V2X bearer indicator indicating a V2X bearer, wherein the V2X bearer is used for a V2X service. Determine that the base station supports only the PC5 based V2X service among the PC5 based V2X service or the Uu based V2X service, withhold resource allocation to the V2X bearer, and the transceiver to the V2X bearer It may be configured to control transmitting information to the mobility management entity (MME) indicating that resource allocation for the resource is suspended.

The context of the V2X bearer may be maintained without being released.

1 shows a structure of an LTE system.

2 shows an air interface protocol of an LTE system for a control plane.

3 shows an air interface protocol of an LTE system for a user plane.

4 shows the structure of a 5G system.

5 shows a reference structure for ProSe.

6 shows a V2X communication environment.

7 illustrates a scenario considered for V2X.

8 shows a dedicated bearer deactivation procedure initiated by the MME.

FIG. 9 is a diagram for describing signaling impact that may occur in a core network when a base station allows a V2X bearer to be released. FIG.

10 shows a bearer resource modification procedure initiated by the terminal.

11 illustrates a service request procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

12 illustrates a service request procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

FIG. 13 illustrates a handover procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

14 illustrates a handover procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

15 illustrates a procedure of starting a Uu-based V2X service according to an embodiment of the present invention.

FIG. 16 illustrates a procedure of switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

17 illustrates a method of performing a V2X communication by a base station according to an embodiment of the present invention.

18 illustrates a method of performing V2X communication by an MME or a terminal according to an embodiment of the present invention.

19 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented by wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA), which employs OFDMA in downlink and SC in uplink -FDMA is adopted. LTE-A (advanced) is the evolution of 3GPP LTE. 5G communication system is the evolution of LTE-A.

For clarity, the following description focuses on LTE-A, but the technical spirit of the present invention is not limited thereto.

1 shows a structure of an LTE system. Communication networks are widely deployed to provide various communication services such as IMS and Voice over internet protocol (VoIP) over packet data.

Referring to FIG. 1, an LTE system structure includes one or more UEs 10, an evolved-UMTS terrestrial radio access network (E-UTRAN), and an evolved packet core (EPC). The terminal 10 is a communication device moved by a user. The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device.

The E-UTRAN may include one or more evolved node-eB (eNB) 20, and a plurality of terminals may exist in one cell. The eNB 20 provides an end point of a control plane and a user plane to the terminal. The eNB 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to in other terms such as a base station (BS), a base transceiver system (BTS), an access point, and the like. . One eNB 20 may be arranged per cell. There may be one or more cells within the coverage of the eNB 20. One cell may be configured to have one of bandwidths such as 1.25, 2.5, 5, 10, and 20 MHz to provide downlink (DL) or uplink (UL) transmission service to various terminals. In this case, different cells may be configured to provide different bandwidths.

Hereinafter, DL means communication from the eNB 20 to the terminal 10, and UL means communication from the terminal 10 to the eNB 20. In the DL, the transmitter may be part of the eNB 20 and the receiver may be part of the terminal 10. In the UL, the transmitter may be part of the terminal 10 and the receiver may be part of the eNB 20.

The EPC may include a mobility management entity (MME) that serves as a control plane, and a system architecture evolution (SAE) gateway (S-GW) that serves as a user plane. The MME / S-GW 30 may be located at the end of the network and is connected to an external network. The MME has information about the access information of the terminal or the capability of the terminal, and this information may be mainly used for mobility management of the terminal. S-GW is a gateway having an E-UTRAN as an endpoint. The MME / S-GW 30 provides the terminal 10 with the endpoint of the session and the mobility management function. The EPC may further include a packet data network (PDN) -gateway (GW). PDN-GW is a gateway with PDN as an endpoint.

The MME includes non-access stratum (NAS) signaling to the eNB 20, NAS signaling security, access stratum (AS) security control, inter CN (node network) signaling for mobility between 3GPP access networks, idle mode terminal reachability ( Control and execution of paging retransmission), tracking area list management (for terminals in idle mode and active mode), P-GW and S-GW selection, MME selection for handover with MME change, 2G or 3G 3GPP access Bearer management, including roaming, authentication, and dedicated bearer settings, SGSN (serving GPRS support node) for handover to the network, public warning system (ETWS) and commercial mobile alarm system (PWS) It provides various functions such as CMAS) and message transmission support. S-GW hosts can be based on per-user packet filtering (eg, through deep packet inspection), legal blocking, terminal IP (Internet protocol) address assignment, transport level packing marking in DL, UL / DL service level charging, gating and It provides various functions of class enforcement, DL class enforcement based on APN-AMBR. For clarity, the MME / S-GW 30 is simply represented as a "gateway", which may include both MME and S-GW.

An interface for user traffic transmission or control traffic transmission may be used. The terminal 10 and the eNB 20 may be connected by the Uu interface. The eNBs 20 may be interconnected by an X2 interface. Neighboring eNBs 20 may have a mesh network structure by the X2 interface. The eNBs 20 may be connected with the EPC by the S1 interface. The eNBs 20 may be connected to the EPC by the S1-MME interface and may be connected to the S-GW by the S1-U interface. The S1 interface supports a many-to-many-relation between eNB 20 and MME / S-GW 30.

The eNB 20 may select for the gateway 30, routing to the gateway 30 during radio resource control (RRC) activation, scheduling and transmission of paging messages, scheduling channel information (BCH), and the like. Perform connection mobility control in transmission, dynamic allocation of resources from the UL and DL to the terminals 10, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC) and LTE activation can do. As mentioned above, the gateway 30 may perform paging initiation, LTE idle state management, user plane encryption, SAE bearer control, and encryption and integrity protection functions of NAS signaling in the EPC.

2 shows an air interface protocol of an LTE system for a control plane. 3 shows an air interface protocol of an LTE system for a user plane.

The layer of the air interface protocol between the UE and the E-UTRAN is based on the lower three layers of the open system interconnection (OSI) model, which is well known in communication systems, and includes L1 (first layer), L2 (second layer), and L3 (third layer). Hierarchical). The air interface protocol between the UE and the E-UTRAN may be horizontally divided into a physical layer, a data link layer, and a network layer, and vertically a protocol stack for transmitting control signals. ) Can be divided into a control plane and a user plane which is a protocol stack for transmitting data information. Layers of the radio interface protocol may exist in pairs in the UE and the E-UTRAN, which may be responsible for data transmission of the Uu interface.

The physical layer (PHY) belongs to L1. The physical layer provides an information transmission service to a higher layer through a physical channel. The physical layer is connected to a higher layer of a media access control (MAC) layer through a transport channel. Physical channels are mapped to transport channels. Data may be transmitted between the MAC layer and the physical layer through a transport channel. Data between different physical layers, that is, between the physical layer of the transmitter and the physical layer of the receiver may be transmitted using radio resources through a physical channel. The physical layer may be modulated using an orthogonal frequency division multiplexing (OFDM) scheme, and utilizes time and frequency as radio resources.

The physical layer uses several physical control channels. A physical downlink control channel (PDCCH) reports resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH to the UE. The PDCCH may carry an uplink grant to report to the UE regarding resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for the PDCCH and is transmitted every subframe. A physical hybrid ARQ indicator channel (PHICH) carries a HARQ ACK (non-acknowledgement) / NACK (non-acknowledgement) signal for UL-SCH transmission. A physical uplink control channel (PUCCH) carries UL control information such as HARQ ACK / NACK, a scheduling request, and a CQI for downlink transmission. The physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH).

The physical channel includes a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe consists of a plurality of symbols in the time domain. One subframe consists of a plurality of resource blocks (RBs). One resource block is composed of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols of the corresponding subframe for the PDCCH. For example, the first symbol of the subframe may be used for the PDCCH. The PDCCH may carry dynamically allocated resources, such as a physical resource block (PRB) and modulation and coding schemes (MCS). A transmission time interval (TTI), which is a unit time at which data is transmitted, may be equal to the length of one subframe. One subframe may have a length of 1 ms.

The transport channel is classified into a common transport channel and a dedicated transport channel depending on whether the channel is shared or not. A DL transport channel for transmitting data from a network to a UE includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, and a DL-SCH for transmitting user traffic or control signals. And the like. The DL-SCH supports dynamic link adaptation and dynamic / semi-static resource allocation by varying HARQ, modulation, coding and transmit power. In addition, the DL-SCH may enable the use of broadcast and beamforming throughout the cell. System information carries one or more system information blocks. All system information blocks can be transmitted in the same period. Traffic or control signals of a multimedia broadcast / multicast service (MBMS) are transmitted through a multicast channel (MCH).

The UL transport channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message, a UL-SCH for transmitting user traffic or a control signal, and the like. The UL-SCH can support dynamic link adaptation due to HARQ and transmit power and potential changes in modulation and coding. In addition, the UL-SCH may enable the use of beamforming. RACH is generally used for initial connection to a cell.

The MAC layer belonging to L2 provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The MAC layer provides a mapping function from a plurality of logical channels to a plurality of transport channels. The MAC layer also provides a logical channel multiplexing function by mapping from multiple logical channels to a single transport channel. The MAC sublayer provides data transfer services on logical channels.

The logical channel may be divided into a control channel for information transmission in the control plane and a traffic channel for information transmission in the user plane according to the type of information to be transmitted. That is, a set of logical channel types is defined for other data transfer services provided by the MAC layer. The logical channel is located above the transport channel and mapped to the transport channel.

The control channel is used only for conveying information in the control plane. The control channel provided by the MAC layer includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a dedicated control channel (DCCH). BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel used for transmitting paging information and paging a terminal whose cell-level location is not known to the network. CCCH is used by the terminal when there is no RRC connection with the network. MCCH is a one-to-many downlink channel used to transmit MBMS control information from the network to the terminal. DCCH is a one-to-one bidirectional channel used by the terminal for transmitting dedicated control information between the terminal and the network in an RRC connection state.

The traffic channel is used only for conveying information in the user plane. The traffic channel provided by the MAC layer includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). DTCH is used for transmission of user information of one UE in a one-to-one channel and may exist in both uplink and downlink. MTCH is a one-to-many downlink channel for transmitting traffic data from the network to the terminal.

The uplink connection between the logical channel and the transport channel includes a DCCH that can be mapped to the UL-SCH, a DTCH that can be mapped to the UL-SCH, and a CCCH that can be mapped to the UL-SCH. The downlink connection between the logical channel and the transport channel is a BCCH that can be mapped to a BCH or DL-SCH, a PCCH that can be mapped to a PCH, a DCCH that can be mapped to a DL-SCH, a DTCH that can be mapped to a DL-SCH, MCCH that can be mapped to MCH and MTCH that can be mapped to MCH.

The RLC layer belongs to L2. The function of the RLC layer includes adjusting the size of the data by segmentation / concatenation of the data received from the upper layer in the radio section such that the lower layer is suitable for transmitting data. In order to guarantee the various QoS required by the radio bearer (RB), the RLC layer is divided into three modes: transparent mode (TM), unacknowledged mode (UM) and acknowledged mode (AM). Provides three modes of operation. AM RLC provides retransmission through automatic repeat request (ARQ) for reliable data transmission. Meanwhile, the function of the RLC layer may be implemented as a functional block inside the MAC layer, in which case the RLC layer may not exist.

The packet data convergence protocol (PDCP) layer belongs to L2. The PDCP layer introduces an IP packet, such as IPv4 or IPv6, over a relatively low bandwidth air interface to provide header compression that reduces unnecessary control information so that the transmitted data is transmitted efficiently. Header compression improves transmission efficiency in the wireless section by transmitting only the information necessary for the header of the data. In addition, the PDCP layer provides security. Security functions include encryption to prevent third party inspection and integrity protection to prevent third party data manipulation.

The radio resource control (RRC) layer belongs to L3. The RRC layer at the bottom of L3 is defined only in the control plane. The RRC layer serves to control radio resources between the terminal and the network. To this end, the UE and the network exchange RRC messages through the RRC layer. The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of RBs. RB is a logical path provided by L1 and L2 for data transmission between the terminal and the network. That is, RB means a service provided by L2 for data transmission between the UE and the E-UTRAN. Setting up an RB means defining the characteristics of the radio protocol layer and channel to provide a particular service, and determining each specific parameter and method of operation. RBs may be classified into two types: signaling RBs (SRBs) and data RBs (DRBs). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

Referring to FIG. 2, the RLC and MAC layers (end at the eNB at the network side) may perform functions such as scheduling, ARQ and HARQ. The RRC layer (ended at the eNB at the network side) may perform functions such as broadcast, paging, RRC connection management, RB control, mobility function, and UE measurement report / control. The NAS control protocol (terminated at the gateway's MME at the network side) may perform functions such as SAE bearer management, authentication, LTE_IDLE mobility handling, paging initiation at LTE_IDLE, and security control for signaling between the terminal and the gateway.

Referring to FIG. 3, the RLC and MAC layer (end at the eNB at the network side) may perform the same function as the function in the control plane. The PDCP layer (terminating at the eNB at the network side) may perform user plane functions such as header compression, integrity protection and encryption.

Hereinafter, the RRC state and the RRC connection method of the UE will be described.

The RRC state indicates whether the RRC layer of the UE is logically connected with the RRC layer of the E-UTRAN. The RRC state may be divided into two types, such as an RRC connected state (RRC_CONNECTED) and an RRC idle state (RRC_IDLE). When the RRC connection between the RRC layer of the terminal and the RRC layer of the E-UTRAN is established, the terminal is in the RRC connection state, otherwise the terminal is in the RRC idle state. Since the terminal of the RRC_CONNECTED has an RRC connection with the E-UTRAN, the E-UTRAN can grasp the existence of the terminal of the RRC_CONNECTED and can effectively control the terminal. Meanwhile, the E-UTRAN cannot grasp the terminal of the RRC_IDLE, and manages the terminal in units of a tracking area in which a core network (CN) is larger than a cell. That is, the terminal of the RRC_IDLE is only identified as a unit of a larger area, and in order to receive a normal mobile communication service such as voice or data communication, the terminal must transition to RRC_CONNECTED.

In the RRC_IDLE state, while the terminal designates a discontinuous reception (DRX) set by the NAS, the terminal may receive a broadcast of system information and paging information. In addition, the terminal may be assigned an identification (ID) that uniquely designates the terminal in the tracking area, and perform public land mobile network (PLMN) selection and cell reselection. In addition, in the RRC_IDLE state, no RRC context is stored in the eNB.

In the RRC_CONNECTED state, the UE may have an E-UTRAN RRC connection and an RRC context in the E-UTRAN to transmit data to the eNB and / or receive data from the eNB. In addition, the terminal may report channel quality information and feedback information to the eNB. In the RRC_CONNECTED state, the E-UTRAN may know the cell to which the UE belongs. Therefore, the network may transmit data to the terminal and / or receive data from the terminal, and the network may inter-RAT with a GSM EDGE radio access network (GERAN) through mobility of the terminal (handover and network assisted cell change (NACC)). radio access technology (cell change indication), and the network may perform cell measurement for a neighboring cell.

In the RRC_IDLE state, the UE designates a paging DRX cycle. In more detail, the UE monitors a paging signal at a specific paging occasion for each UE specific paging DRX cycle. Paging opportunity is the time interval during which the paging signal is transmitted. The terminal has its own paging opportunity.

The paging message is sent across all cells belonging to the same tracking area. If the terminal moves from one tracking area to another tracking area, the terminal sends a tracking area update (TAU) message to the network to update the location.

When the user first turns on the power of the terminal, the terminal first searches for an appropriate cell and then stays in RRC_IDLE in that cell. When it is necessary to establish an RRC connection, the terminal staying in the RRC_IDLE may make an RRC connection with the RRC of the E-UTRAN through the RRC connection procedure and may transition to the RRC_CONNECTED. The UE staying in RRC_IDLE needs to establish an RRC connection with the E-UTRAN when uplink data transmission is necessary due to a user's call attempt or when a paging message is received from the E-UTRAN and a response message is required. Can be.

In order to manage mobility of the UE in the NAS layer, two states of EMM-REGISTERED (EPS Mobility Management-REGISTERED) and EMM-DEREGISTERED are defined, and these two states are applied to the UE and the MME. The initial terminal is in the EMM-DEREGISTERED state, and the terminal performs a process of registering with the corresponding network through an initial attach procedure to access the network. If the attach procedure is successfully performed, the UE and the MME are in the EMM-REGISTERED state.

In order to manage a signaling connection between the UE and the EPC, two states are defined, an EPS Connection Management (ECM) -IDLE state and an ECM-CONNECTED state, and these two states are applied to the UE and the MME. When the UE in the ECM-IDLE state establishes an RRC connection with the E-UTRAN, the UE is in the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN. When the terminal is in the ECM-IDLE state, the E-UTRAN does not have the context information of the terminal. Accordingly, the UE in the ECM-IDLE state performs a terminal-based mobility related procedure such as cell selection or cell reselection without receiving a command from the network. On the other hand, when the terminal is in the ECM-CONNECTED state, the mobility of the terminal is managed by the command of the network. In the ECM-IDLE state, if the position of the terminal is different from the position known by the network, the terminal informs the network of the corresponding position of the terminal through a tracking area update procedure.

Hereinafter, the 5G network structure will be described.

4 shows the structure of a 5G system.

In the case of an Evolved Packet Core (EPC), which is a core network structure of an existing Evolved Packet System (EPS), an entity such as a mobility management entity (MME), a serving gateway (S-GW), and a packet data network gateway (P-GW) Each function, reference point, protocol, etc. are defined.

On the other hand, in the case of a 5G core network (or NextGen core network), functions, reference points, protocols, etc. are defined for each network function (NF). That is, 5G core network does not define functions, reference points, protocols, etc. for each entity.

Referring to FIG. 4, the 5G system structure includes one or more UEs 10, a Next Generation-Radio Access Network (NG-RAN), and a Next Generation Core (NGC).

The NG-RAN may include one or more gNBs 40, and a plurality of terminals may exist in one cell. The gNB 40 provides the terminal with the control plane and the end point of the user plane. The gNB 40 generally refers to a fixed station communicating with the terminal 10 and may be referred to as other terms such as a base station (BS), a base transceiver system (BTS), an access point, and the like. . One gNB 40 may be arranged per cell. There may be one or more cells within coverage of the gNB 40.

The NGC may include an Access and Mobility Function (AMF) and a Session Management Function (SMF) that are responsible for the functions of the control plane. The AMF may be responsible for the mobility management function, and the SMF may be responsible for the session management function. The NGC may include a user plane function (UPF) that is responsible for the function of the user plane.

An interface for user traffic transmission or control traffic transmission may be used. Terminal 10 and gNB 40 may be connected by an NG3 interface. The gNBs 40 may be interconnected by Xn interface. Neighboring gNBs 40 may have a mesh network structure with an Xn interface. The gNBs 40 may be connected to the NGC by the NG interface. The gNBs 40 may be connected to the AMF by the NG-C interface and may be connected to the UPF by the NG-U interface. The NG interface supports a many-to-many-relation between gNB 40 and MME / UPF 50.

The gNB host may determine functions for radio resource management, IP header compression and encryption of user data stream, and routing to AMF from information provided by the terminal. Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE, Routing of User Plane data to one or more UPFs towards UPF (s)), Scheduling and transmission of paging messages (originated from the AMF), transmission and scheduling of system broadcast information (derived from AMF or O & M) Scheduling and transmission of system broadcast information (originated from the AMF or O & M), or setting up and measuring measurement reports for scheduling and mobility (Me It can perform functions such as asurement and measurement reporting configuration for mobility and scheduling.

Access and Mobility Function (AMF) hosts can be used for NAS signaling termination, NAS signaling security, AS Security control, and inter CN node signaling for mobility between 3GPP access networks. node signaling for mobility between 3GPP access networks), IDLE mode UE reachability (including control and execution of paging retransmission), UE in ACTIVE mode and IDLE mode Tracking Area list management (for UE in idle and active mode), AMF selection for handovers with AMF change, Access Authentication, Or perform key functions such as access authorization including check of roaming rights. The.

A user plane function (UPF) host is an anchor point for Intra- / Inter-RAT mobility (when applicable), an external PDU session point for the interconnection to the data network (if applicable). (External PDU session point of interconnect to Data Network), Packet routing & forwarding, Packet inspection and User plane part of Policy rule enforcement, Traffic usage reporting ( Traffic usage reporting, Uplink classifier to support routing traffic flows to a data network, Branching point to support multi- homed PDU session, QoS handling for the user plane, e.g. packet filtering, gating, QoS handling for user plane, eg packet filtering, gating, UL / DL rate enforcement, uplink traffic verification (SDF to QoS flow mapping), transport level packet marking in downlink and uplink It can perform main functions such as packet marking in the uplink and downlink, or downlink packet buffering and downlink data notification triggering.

The Session Management Function (SMF) host is responsible for session management, UE IP address allocation and management, selection and control of UP functions, and traffic to the appropriate destinations. Configure traffic steering at UPF to route traffic to proper destination, control part of policy enforcement and QoS, or downlink data notification Can perform key functions such as

Below, D2D  The operation will be described.

In 3GPP LTE-A, a service related to D2D operation is called proximity based services (ProSe). Hereinafter, ProSe is an equivalent concept to D2D operation, and ProSe may be mixed with D2D operation. Hereinafter, ProSe is described. ProSe has ProSe communication and ProSe direct discovery.

ProSe direct communication refers to communication performed between two or more neighboring terminals. The terminals may perform communication using a user plane protocol. ProSe-enabled UE refers to a terminal that supports a procedure related to the requirements of ProSe. Unless otherwise noted, ProSe capable terminals include both public safety UEs and non-public safety UEs. The public safety terminal is a terminal that supports both a public safety-specific function and a ProSe process. A non-public safety terminal is a terminal that supports a ProSe process but does not support a function specific to public safety.

ProSe direct discovery is a process for ProSe capable terminals to discover other ProSe capable terminals that are adjacent to each other, using only the capabilities of the two ProSe capable terminals. EPC-level ProSe discovery refers to a process in which an EPC determines whether two ProSe capable terminals are in proximity and informs the two ProSe capable terminals of their proximity. For convenience, ProSe direct communication may be referred to as D2D communication, and ProSe direct discovery may be referred to as D2D discovery.

Below, ProSe  Radio resource allocation for direct communication will now be described.

ProSe capable terminal may use the following two modes for resource allocation for ProSe direct communication.

1) Mode 1: A mode in which resources for ProSe direct communication are scheduled from a base station. In order to transmit data in mode 1, the UE must be in an RRC_CONNECTED state. The terminal requests the base station for transmission resources, and the base station schedules resources for scheduling allocation and data transmission. The terminal may transmit a scheduling request to the base station and may transmit a ProSe BSR (Buffer Status Report). Based on the ProSe BSR, the base station determines that the terminal has data for ProSe direct communication and needs resources for this transmission.

2) Mode 2: A mode in which a terminal directly selects a resource. The terminal selects a resource for direct ProSe direct communication from a resource pool. The resource pool may be set or predetermined by the network.

On the other hand, when the terminal has a serving cell, that is, the terminal is in the RRC_CONNECTED state with the base station or located in a specific cell in the RRC_IDLE state, the terminal is considered to be within the coverage of the base station. If the terminal is out of coverage, only mode 2 may be applied. If the terminal is in coverage, mode 1 or mode 2 may be used depending on the configuration of the base station. If there is no other exceptional condition, the terminal may change the mode from mode 1 to mode 2 or from mode 2 to mode 1 only when the base station is configured.

5 shows a reference structure for ProSe.

Referring to FIG. 5, the reference structure for ProSe includes a plurality of terminals including an E-UTRAN, an EPC, and a ProSe application program, a ProSe application server, and a ProSe function. EPC represents the E-UTRAN core network structure. The EPC may include an MME, S-GW, P-GW, policy and charging rules function (PCRF), home subscriber server (HSS), and the like. ProSe application server is a user of ProSe ability to create application functions. The ProSe application server may communicate with an application program in the terminal. An application program in the terminal may use a ProSe capability for creating an application function.

The ProSe function may include at least one of the following, but is not necessarily limited thereto.

Interworking via a reference point towards the 3rd party applications

Authentication and configuration of the UE for discovery and direct communication

Enable the functionality of the EPC level ProSe discovery

ProSe related new subscriber data and handling of data storage, and also handling of ProSe identities

Security related functionality

Provide control towards the EPC for policy related functionality

Provide functionality for charging (via or outside of EPC, e.g., offline charging)

Below, ProSe  Reference points and reference interfaces are described in the reference structure.

PC1: This is a reference point between a ProSe application in a terminal and a ProSe application in a ProSe application server. This is used to define signaling requirements at the application level.

PC2: Reference point between ProSe application server and ProSe function. This is used to define the interaction between the ProSe application server and ProSe functionality. An application data update of the ProSe database of the ProSe function may be an example of the interaction.

PC3: Reference point between the terminal and the ProSe function. Used to define the interaction between the UE and the ProSe function. The setting for ProSe discovery and communication may be an example of the interaction.

PC4: Reference point between the EPC and ProSe functions. It is used to define the interaction between the EPC and ProSe functions. The interaction may exemplify when establishing a path for 1: 1 communication between terminals, or when authenticating a ProSe service for real time session management or mobility management.

PC5: Reference point for using the control / user plane for discovery and communication, relay, and 1: 1 communication between terminals.

PC6: Reference point for using features such as ProSe discovery among users belonging to different PLMNs.

SGi: can be used for application data and application level control information exchange.

Below, V2X (vehicle to everything) Discuss communication.

6 shows a V2X communication environment.

V2X is a technology that adds mobility to D2D technology, allowing vehicles to continue to communicate with road infrastructure and other vehicles as they drive, exchanging and sharing useful information such as traffic conditions. The connectivity function is being applied mainly to some models, and vehicle-to-infrastructure (V2V), vehicle-to-infrastructure (V2I) communication, Research continues to support vehicle-to-pedestrian (V2P) and vehicle-to-network (V2N) communications.

According to the V2X communication, the vehicle continuously broadcasts information about its position, speed, direction, and the like. The surrounding vehicle that receives the broadcasted information recognizes the movement of the vehicles around itself and utilizes it for accident prevention. In other words, similarly to an individual having a terminal having a form of a smart phone or a smart watch, a specific type of terminal may be installed in each vehicle. At this time, the terminal installed in the vehicle is a device that receives the actual communication service in the communication network. For example, a terminal installed in a vehicle may access a base station in an E-UTRAN and receive a communication service.

7 illustrates a scenario considered for V2X.

Referring to FIG. 7 (a), a scenario in which only a PC5-based V2X service, which is an interface between terminals, is supported may be considered for V2X. Referring to FIG. 7B, a scenario of supporting only Uu-based V2X service, which is an interface between a base station and a terminal, may be considered for V2X. Referring to FIG. 7C, a scenario supporting both PC5 and Uu based V2X services may be considered for V2X. The base station may switch the V2X bearer from Uu to PC5. That is, the base station may switch the Uu based V2X service to the PC5 based V2X service.

On the other hand, when the load of the Uu interface is high or the Uu interface is overloaded, if the base station can know which bearer is used for V2X service, the base station triggers the release of the associated bearer if necessary, and the terminal more PC5 resources It may be possible to provide. For example, the base station can know which bearer is used for V2X service by receiving an indicator indicating a V2X bearer. However, in the case of release of a bearer triggered by a base station, the following problem may occur.

If the base station wants to release the bearer for the V2X service, the MME Initiated Dedicated Bearer Deactivation procedure initiated by the MME may be used. In this specification, a bearer for a V2X service means a bearer used for a V2X service or a bearer to be used for a V2X service, and may be referred to as a V2X bearer for convenience of description. The dedicated bearer deactivation procedure initiated by the MME is described in detail in Section 5.4.4.2 MME Initiated Dedicated Bearer Deactivation in 3GPP TS 23.401 V13.6.1 (2016-03).

8 shows a dedicated bearer deactivation procedure initiated by the MME.

Referring to FIG. 8, in step S800, the radio bearer for the UE in the ECM_CONNECTED state is local for reasons such as abnormal resource limitation or radio where the base station is not allowed to maintain all GBR bearers assigned thereto. Condition) can be released. However, the non-GBR bearer is not released by the base station unless an error situation occurs. QCI characteristics for GBR bearers and non-GBR bearers can be shown in Table 1.

QCI	Resource Type	Priority level	Packet Delay Budget	Packet Error Loss Rate	Example Services
75	GBR	1.8	50 ms	10-2	V2X messages
79	Non-GBR	5.8	50 ms	10-2	V2X messages

That is, except for an error condition of the base station, the base station does not release the non-GBR bearer. Meanwhile, the bearer used for the V2X service is mainly a non-GBR bearer carrying a CAM message. Therefore, according to the dedicated bearer deactivation procedure initiated by the MME, even if the base station knows which bearer is used for the V2X service, if the load of the Uu interface is high or the Uu interface is overloaded, the base station may perform It may not trigger the release. This is because, in the dedicated bearer deactivation procedure initiated by the MME, the base station can trigger the release of the non-GBR bearer only in an error situation.

If a V2X bearer is allowed to be released by the base station using a dedicated bearer deactivation procedure initiated by the MME, there may be a signaling impact in the core network if it creates or releases a V2X bearer.

FIG. 9 is a diagram for describing signaling impact that may occur in a core network when a base station allows a V2X bearer to be released. FIG.

It is assumed that the terminal can transmit a V2X message through the Uu interface. The base station may have one of 'Uu only', 'PC5 only', and 'both Uu and PC5' for V2X transmission. 'Uu only' is a setting where the base station supports only Uu-based V2X service, 'PC5 only' is a setting where the base station supports only PC5-based V2X service, and 'both Uu and PC5' is a base station based on Uu It means not only V2X service but also PC5-based V2X service.

Referring to FIG. 9, the setting for V2X transmission of the first base station may be changed from 'both Uu and PC5' to 'PC5 only'. Accordingly, the first base station may release the V2X bearer of the terminal using a dedicated bearer deactivation procedure initiated by the MME. However, if there are a plurality of terminals transmitting V2X messages through the Uu interface within the coverage of the first base station, signaling between networks for releasing the V2X bearer may increase rapidly according to the number of terminals.

Furthermore, signaling impact in the core network may occur even when the base station newly creates a V2X bearer.

Referring to FIG. 9, the terminal may move to the second base station, and the setting for V2X transmission of the second base station may be 'both Uu and PC5'. Accordingly, the terminal may request the network to create a V2X bearer carrying a V2X message through the Uu interface. To this end, the terminal may initiate a UE requested bearer resource modification procedure initiated by the terminal. The bearer resource modification procedure initiated by the terminal is described in detail in 3GPP TS 23.401 V13.6.1 (2016-03) section 5.4.5 UE requested bearer resource modification.

10 shows a bearer resource modification procedure initiated by the terminal.

Referring to FIG. 10, in order for a terminal to create a V2X bearer, much signaling may be required between network entities. If the number of terminals moving from the first base station to the second base station increases, this may require more signaling in the core network.

Thus, depending on the configuration of the base station's V2X transmission, the base station's releasing or setting up a particular V2X bearer may impose signaling burden between networks.

Meanwhile, when the load of the Uu interface is high or the Uu interface is overloaded, the base station may broadcast that the setting for the V2X transmission is set to 'PC5 only'. Since the UE that receives the 'PC5 only' setting knows that the V2X message cannot be transmitted through the Uu interface, the base station may not transmit the V2X message using the V2X bearer. In this situation, since no traffic is carried over the V2X bearer, it is not a problem that the V2X bearer is not released. A bearer (ie, a V2X bearer) created for the transmission of a V2X service (eg, a CAM message) can always be used while the terminal is located in a network supporting the V2X service, so that the terminal supports the V2X service. While located at, the V2X bearer does not need to be released. This is because releasing the V2X bearer may cause signaling overhead. Hereinafter, a method of maintaining a V2X bearer and an apparatus supporting the same according to an embodiment of the present invention will be described.

11 illustrates a service request procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

Referring to FIG. 11, in step S1101, the terminal may trigger a service request procedure to transmit uplink data on Uu. The terminal may be a V2X capable UE.

In step S1102, the terminal may transmit a NAS message service request encapsulated in an RRC connection setup complete message to the base station.

In step S1103, the base station may transmit a NAS message service request including an initial UE message message to the MME / AMF.

In step S1104, when the MME / AMF receives the message, the MME / AMF may send an Initial Context Setup Request message to the base station. The initial context setup request message may include a bearer indication for V2X. The bearer indicator for the V2X may indicate whether the requested bearer is a V2X bearer. In this specification, a bearer indicator for V2X may be referred to as a V2X bearer indicator.

In step S1105, the base station may determine whether any one of the settings 'Uu only', 'PC5 only' and 'both Uu and PC5' for the V2X transmission. When the base station is set to 'PC5 only' and receives an initial context setup request message containing a V2X bearer indicator for the requested bearer, the base station stores the V2X bearer indicator for each V2X bearer and will not allocate resources to the V2X bearer. Can be. That is, the base station may withhold resource allocation for the V2X bearer.

In step S1106, the base station may respond with an Initial Context Setup Response message. The initial context setup response message may include an E-RAB failed to setup list, and the E-RAB failed to setup list may include a new cause value. The E-RAB Failed to Setup List may be a list of IDs of the E-RAB that have not been successfully established. The new cause value may indicate that the base station has not allocated a resource for the V2X bearer. The new cause value may indicate that the base station has suspended resource allocation for the V2X bearer.

In step S1107, if the new cause value is included in the E-RAB Failed to Setup List, the MME / AMF may not deactivate the bearer context included in the received E-RAB Failed to Setup List. That is, the MME / AMF receiving the E-RAB Failed to Setup List including the new cause value may maintain the bearer context included in the E-RAB Failed to Setup List.

In step S1108, the base station may transmit an RRC connection reconfiguration message to the terminal. The RRC connection reconfiguration message may include an indicator indicating that the base station has not allocated resources to the V2X bearer. The RRC connection reestablishment message may include an indicator indicating that the base station has suspended resource allocation for the V2X bearer. In addition, the indicator may include bearer related information. For example, the bearer related information may be a bearer identifier (ID).

In step S1109, if the indicator is included in the RRC connection reestablishment message, the terminal may not reactivate and deactivate the indicated bearer context.

12 illustrates a service request procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

Referring to FIG. 12, in step S1201, the terminal may trigger a service request procedure to transmit uplink data on Uu. The terminal may be a V2X capable UE.

In step S1202, the terminal may transmit a NAS message service request encapsulated in an RRC connection setup complete message to the base station.

In step S1203, the base station may transmit a NAS message service request including an initial UE message message to the MME / AMF.

In step S1204, when the MME / AMF receives the message, the MME / AMF may send an Initial Context Setup Request message to the base station. The initial context setup request message may include a V2X bearer indicator. The V2X bearer indicator may indicate whether the requested bearer is a V2X bearer.

In step S1205, the base station may determine whether any one of the settings 'Uu only', 'PC5 only' and 'both Uu and PC5' for V2X transmission. When the base station is set to 'PC5 only' and receives an initial context setup request message containing a V2X bearer indicator for the requested bearer, the base station stores the V2X bearer indicator for each V2X bearer and will not allocate resources to the V2X bearer. Can be. That is, the base station may withhold resource allocation for the V2X bearer.

In step S1206, the base station may respond with an Initial Context Setup Response message. The initial context setup response message may include an E-RAB failed to setup list, and the E-RAB failed to setup list may include a new cause value. The E-RAB Failed to Setup List may be a list of IDs of the E-RAB that have not been successfully established. The new cause value may indicate that the base station has not allocated a resource for the V2X bearer. The new cause value may indicate that the base station has suspended resource allocation for the V2X bearer.

In step S1207, if the new cause value is included in the E-RAB Failed to Setup List, the MME / AMF may perform marking on the bearer included in the E-RAB Failed to Setup List. For example, the MME / AMF may mark 'pending' on bearers included in the E-RAB Failed to Setup List. The MME / AMF may not deactivate the bearer context included in the received E-RAB Failed to Setup List. Therefore, the MME / AMF receiving the E-RAB Failed to Setup List including the new cause value may maintain the bearer context included in the E-RAB Failed to Setup List.

In step S1208, the base station may transmit an RRC connection reconfiguration message to the terminal. The RRC connection reconfiguration message may include an indicator indicating that the base station has not allocated resources to the V2X bearer. The RRC connection reestablishment message may include an indicator indicating that the base station has suspended resource allocation for the V2X bearer. In addition, the indicator may include bearer related information. For example, the bearer related information may be a bearer identifier (ID).

In step S1209, if the indicator is included in the RRC connection reconfiguration message, the terminal may perform marking on the bearer included in the failed list. For example, the terminal may mark 'pending' on the bearer included in the E-RAB Failed to Setup List. And, the terminal may not deactivate the EPS bearer context for the marked bearer. Accordingly, the terminal receiving the RRC connection reconfiguration message including the indicator may maintain the context of the V2X bearer. Additionally, the terminal may not transmit data on the marked bearer.

FIG. 13 illustrates a handover procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

Referring to FIG. 13, in step S1301, the terminal may transmit a measurement reports message to the source base station.

In step S1302, the source base station may determine the handover based on the received measurement report.

In operation S1303, the source base station may transmit a handover request message to the target base station. The handover request message may include a V2X bearer indicator. The V2X bearer indicator may indicate whether the requested bearer is a V2X bearer.

In operation S1304, the target base station may determine whether one of 'Uu only', 'PC5 only', and 'both Uu and PC5' has a setting for V2X transmission. When the target base station is set to 'PC5 only' and receives a handover request message containing a V2X bearer indicator for the requested bearer, the target base station stores the V2X bearer indicator for each V2X bearer and does not allocate resources to the V2X bearer. You may not. That is, the target base station may withhold resource allocation for the V2X bearer.

In operation S1305, the target base station that has received the handover request message may transmit a handover request acknowledgment message to the source base station in response thereto. The handover request approval message may include an E-RABs Admitted List or an E-RABs Not Admitted List, and the E-RABs Admitted List or E-RABs Not Admitted List may include new cause values, respectively. The handover request approval message may include an indicator. The new cause value or indicator may indicate that the target base station has not allocated resources for the V2X bearer. The new cause value or indicator may indicate that the target base station has suspended resource allocation for the V2X bearer.

In step S1306, when the source base station receives a message from the target base station, the source base station may transmit an RRC Connection Reconfiguration message to the terminal. The RRC connection reconfiguration message may include an indicator indicating that the base station has not allocated resources to the V2X bearer. The RRC connection reestablishment message may include an indicator indicating that the base station has suspended resource allocation for the V2X bearer. In addition, the indicator may include bearer related information. For example, the bearer related information may be a bearer identifier (ID).

In step S1307, when the terminal receives a message from the source base station, the terminal may perform a detach.

In step S1308, the terminal may not reactivate and deactivate the indicated bearer context.

In step S1309, the terminal may transmit an RRC Connection Reconfiguration Complete message to the target base station.

In step S1310, the target base station may transmit a path switch request message to the MME / AMF. The path switch request message may include an E-RAB To Be Switched in Downlink List, and the E-RAB To Be Switched in Downlink List may include a new cause value. The path switch request message may include an indicator. The new cause value or indicator may indicate that the target base station has not allocated resources for the V2X bearer. The new cause value or indicator may indicate that the target base station has suspended resource allocation for the V2X bearer.

In step S1311, when the MME / AMF receives a message from the target base station, the MME / AMF may not deactivate the bearer context included in the list. For example, an MME / AMF that has received an E-RAB To Be Switched in Downlink List containing a new cause value may maintain a bearer context included in the E-RAB To Be Switched in Downlink List.

In step S1312, the MME / AMF may respond to the target base station with a Path Switch Request Acknowledge message.

In operation S1313, the target base station may transmit a UE context release message to the source base station.

14 illustrates a handover procedure for switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

Referring to FIG. 14, in step S1401, the terminal may transmit a measurement reports message to the source base station.

In step S1402, the source base station may determine the handover based on the received measurement report.

In operation S1403, the source base station may transmit a handover request message to the target base station. The handover request message may include a V2X bearer indicator. The V2X bearer indicator may indicate whether the requested bearer is a V2X bearer.

In operation S1404, the target base station may determine whether one of 'Uu only', 'PC5 only', and 'both Uu and PC5' has a setting for V2X transmission. When the target base station is set to 'PC5 only' and receives a handover request message containing a V2X bearer indicator for the requested bearer, the target base station stores the V2X bearer indicator for each V2X bearer and does not allocate resources to the V2X bearer. You may not. That is, the target base station may withhold resource allocation for the V2X bearer.

In operation S1405, the target base station that has received the handover request message may transmit a handover request acknowledgment message to the source base station in response thereto. The handover request approval message may include an E-RABs Admitted List or an E-RABs Not Admitted List, and the E-RABs Admitted List or E-RABs Not Admitted List may include new cause values, respectively. The handover request approval message may include an indicator. The new cause value or indicator may indicate that the target base station has not allocated resources for the V2X bearer. The new cause value or indicator may indicate that the target base station has suspended resource allocation for the V2X bearer.

In step S1406, when the source base station receives a message from the target base station, the source base station may transmit an RRC connection reconfiguration message to the terminal. The RRC connection reconfiguration message may include an indicator indicating that the base station has not allocated resources to the V2X bearer. The RRC connection reestablishment message may include an indicator indicating that the base station has suspended resource allocation for the V2X bearer. In addition, the indicator may include bearer related information. For example, the bearer related information may be a bearer identifier (ID).

In step S1407, when the terminal receives a message from the source base station, the terminal may perform a detach.

In step S1408, the terminal may perform marking on the bearer included in the failed list and indicated by the new cause value. For example, the terminal may mark 'pending' on the bearer included in the failed list and indicated by the new cause value. And, the terminal may not deactivate the EPS bearer context for the marked bearer. Accordingly, the terminal receiving the RRC connection reconfiguration message including the indicator may maintain the context of the V2X bearer. Additionally, the terminal may not transmit data on the marked bearer.

In step S1409, the terminal may transmit an RRC connection reconfiguration complete message to the target base station.

In step S1410, the target base station may transmit a path switch request message to the MME / AMF. The path switch request message may include an E-RAB To Be Switched in Downlink List, and the E-RAB To Be Switched in Downlink List may include a new cause value. The path switch request message may include an indicator. The new cause value or indicator may indicate that the target base station has not allocated resources for the V2X bearer. The new cause value or indicator may indicate that the target base station has suspended resource allocation for the V2X bearer.

In step S1411, if the new cause value is included in the E-RAB To Be Switched in Downlink List, the MME / AMF performs marking on the bearer indicated by the new cause value included in the E-RAB To Be Switched in Downlink List. can do. Alternatively, when the indicator is included in the path switch request message, the MME / AMF may perform marking on the bearer indicated by the indicator. For example, the MME / AMF may mark 'pending' on bearers included in the E-RAB To Be Switched in Downlink List. The MME / AMF may not deactivate the bearer context included in the list. Accordingly, the MME / AMF may maintain a bearer context included in the E-RAB To Be Switched in Downlink List.

In step S1412, the MME / AMF may respond to the target base station with a Path Switch Request Acknowledge message.

In operation S1413, the target base station may transmit a UE context release message to the source base station.

15 illustrates a procedure of starting a Uu-based V2X service according to an embodiment of the present invention.

Referring to FIG. 15, in step S1501, the P-GW may transmit downlink traffic for V2X to the base station via the S-GW.

In step S1502, the base station may determine whether to establish a DRB for the V2X bearer. For example, if the base station receives data for V2X from the S-GW via S1-U, the base station may decide to establish a DRB for the V2X bearer. For example, the base station receiving the data for the V2X may perform resource allocation for the held V2X bearer to establish a DRB for the V2X bearer.

In step S1503, to set up the DRB for the V2X bearer, the base station may transmit an RRC connection reconfiguration (RRC Connection Reconfiguration) to the terminal.

In step S1504, when the RRC connection reconfiguration message is received from the base station, and the requested DRB is successfully established, the AS layer of the terminal may inform the NAS layer of the terminal that the corresponding DRB was successfully established. Thereafter, the terminal may remove the marking for all bearers. For example, if the requested DRB is successfully established, the terminal may remove the 'pending' marking performed on the bearer in step S1209 of FIG. 12 or step S1408 of FIG. 14.

In operation S1505, the terminal may transmit an RRC connection reconfiguration complete message to the base station.

In step S1506, the base station may transmit information to the MME / AMF indicating that the DRB for the V2X bearer is established. The information indicating that the DRB for the V2X bearer is established may be a DRB Activation Indication message, an existing message, a new IE included in a new message, or a new IE included in an existing message. Upon receiving the information, the MME / AMF may recognize that resources are allocated to the indicated V2X bearer. The MME may then remove the marking for all bearers. For example, the MME / AMF which has received the information indicating that the DRB for the V2X bearer is established may remove the 'pending' marking performed on the bearer in step S1207 of FIG. 12 or step S1411 of FIG. 14.

In step S1507, the base station may transmit data for the V2X to the terminal through the DRB set for the V2X bearer.

FIG. 16 illustrates a procedure of switching between a PC5 based V2X service and a Uu based V2X service according to an embodiment of the present invention.

Referring to FIG. 16, in step S1600, the base station may receive a V2X bearer indicator. The V2X bearer indicator may indicate whether the requested bearer is a V2X bearer. The V2X bearer indicator may be included in an initial context setup request message and received from an MME / AMF. When the base station is a target base station, the V2X bearer indicator may be included in a handover request message and received from a source base station.

In step S1601, the base station may determine whether the base station supports only PC5 based V2X service. The base station may selectively support either or both of the PC5 based V2X service or the Uu based V2X service.

If it is determined in step S1602 that the base station supports only PC5 based V2X service, the base station may store the V2X bearer indicator for the V2X bearer and may not allocate resources to the V2X bearer. That is, the base station may withhold resource allocation for the V2X bearer.

In step S1603, the base station may transmit information indicating that the resource allocation for the V2X bearer by the base station is suspended to the terminal. The information may be at least one of an indicator or a cause value. The information may be included in the RRC connection reconfiguration message and transmitted to the terminal.

In step S1604, the terminal may perform marking on the V2X bearer and maintain the context of the marked V2X bearer. Thus, even though the base station currently provides only PC5 based V2X service, the context of the V2X bearer may be maintained and the V2X bearer may not be released. Further, the terminal may stop data transmission through the V2X bearer.

In step S1605, the base station may transmit information indicating that resource allocation for the V2X bearer by the base station is suspended to the MME / AMF. The information may be at least one of an indicator or a cause value. The information may be included in an initial context setup response message and transmitted to the MME / AMF. The information may be included in the path switch request message and transmitted to the MME / AMF.

In step S1606, the MME / AMF may perform marking on the V2X bearer and maintain the context of the marked V2X bearer. Thus, even though the base station currently provides only PC5 based V2X service, the context of the V2X bearer may be maintained and the V2X bearer may not be released.

The order of steps S1603 / S1604 and S1605 / S1606 can be changed from each other. That is, the base station may transmit information indicating that resource allocation for the V2X bearer by the base station is suspended to the MME / AMF and then to the terminal.

In step S1607, the base station may determine whether the base station supports Uu-based V2X service. If the base station is determined to support Uu-based V2X service, the base station may perform resource allocation for the reserved V2X bearer.

In step S1608, the base station may transmit an RRC connection reset message to the terminal.

In step S1609, the terminal successfully establishing the RRC connection may remove the marking for the V2X bearer.

In step S1610, the terminal may transmit an RRC connection reset complete message to the base station.

In step S1611, the base station may transmit information indicating that the V2X bearer is activated to the MME / AMF.

In step S1612, the MME / AMF may remove the marking for the V2X bearer.

According to an embodiment of the present invention, when the base station sets the configuration for the V2X service to 'PC5 only', the base station may not allocate resources to the bearer to be used for V2X. That is, resource allocation for the V2X bearer can be suspended. The base station may inform the terminal and the MME / AMF that the base station has not allocated resources to the V2X bearer. The MME / AMF may not deactivate the bearer context based on the information received from the base station. The terminal may not attempt to release the indicated radio bearer based on the information received from the base station. Thus, even though the setting for V2X at the base station is 'PC5 only', the V2X bearer may not be released and may be maintained.

Furthermore, when the base station changes the setting for the V2X service to 'Uu only' or 'both Uu and PC5', the base station may activate resource allocation for the V2X bearer, and the terminal may quickly use the maintained V2X bearer. Can receive V2X data.

The procedure proposed in this specification may be applied when the terminal moves to a base station set to 'PC5 only'. The procedure proposed in this specification may be applied to a case where the base station set to 'Uu only' or 'both Uu and PC5' changes the configuration to 'PC5 only'. Furthermore, the proposed procedure can also be applied to signaling between RAN and CN in 5G architecture similar to handover procedure or service request procedure in LTE.

17 illustrates a method of performing a V2X communication by a base station according to an embodiment of the present invention.

Referring to FIG. 17, in step S1710, the base station may receive a V2X bearer indicator indicating a V2X bearer. The V2X bearer may be a bearer used for V2X service.

In operation S1720, the base station may determine that the base station supports only the PC5 based V2X service among the PC5 based V2X service or the Uu based V2X service.

In step S1730, the base station may withhold resource allocation for the V2X bearer. If the base station is determined to support only the PC5 based V2X service, resource allocation for the V2X bearer may be suspended.

In step S1740, the base station may transmit information indicating that the resource allocation for the V2X bearer is suspended to the mobility management entity (MME).

In addition, the base station may transmit information indicating that the resource allocation for the V2X bearer is suspended to the terminal. The base station is a target base station, the information transmitted to the terminal may be transmitted to the terminal via a source base station. The information may include an identifier (ID) of the V2X bearer.

Additionally, the base station may determine that the base station supports the Uu based V2X service, and may allocate resources for the V2X bearer. Thereafter, the base station may establish a DRB for the V2X service based on the resources allocated for the V2X bearer, and transmit information indicating that the DRB for the V2X bearer is established to the MME.

18 illustrates a method of performing V2X communication by an MME or a terminal according to an embodiment of the present invention.

Referring to FIG. 18, in step S1810, the device may receive information from the base station indicating that resource allocation for the V2X bearer is suspended. The V2X bearer may be a bearer used for V2X service. The device may be an MME or a terminal.

In step S1820, the device may perform marking on the V2X bearer instructing to suspend deactivation of the V2X bearer. If the base station supports only the PC5-based V2X service among the PC5-based V2X service or the Uu-based V2X service, resource allocation for the V2X bearer may be suspended by the base station.

In step S1830, the device may maintain the context of the marked V2X bearer.

If the device is an MME, in addition, the device may receive information from the base station indicating that a DRB for the V2X bearer has been established. Upon receiving information indicating that the DRB has been established, the device may remove the marking on the V2X bearer.

If the device is a terminal, the device may additionally receive an RRC connection reconfiguration message from the base station. When the RRC connection reset message is received, the device may remove the marking on the V2X bearer. The AS layer of the terminal may inform the NAS of the terminal that the DRB for the V2X bearer is established.

19 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The terminal 1900 includes a processor 1901, a memory 1902, and a transceiver 1903. The memory 1902 is connected to the processor 1901 and stores various information for driving the processor 1901. The transceiver 1903 is connected to the processor 1901 and transmits and / or receives a radio signal. The processor 1901 implements the proposed functions, processes, and / or methods. In the above-described embodiment, the operation of the terminal may be implemented by the processor 1901.

Base station 1910 includes a processor 1911, a memory 1912, and a transceiver 1913. The memory 1912 is connected to the processor 1911 and stores various information for driving the processor 1911. The transceiver 1913 is coupled to the processor 1911 to transmit and / or receive wireless signals. Processor 1911 implements the proposed functions, processes, and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 1911.

The MME / AMF 1920 includes a processor 1921, a memory 1922, and a transceiver 1923. The memory 1922 is connected to the processor 1921 to store various information for driving the processor 1921. The transceiver 1923 is connected to the processor 1921 to transmit and / or receive a radio signal. The processor 1921 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the MME / AMF may be implemented by the processor 1921.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The transceiver may include baseband circuitry for processing wireless signals. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

Based on the examples described above, various techniques in accordance with the present disclosure have been described with reference to the drawings and reference numerals. For convenience of description, each technique described a number of steps or blocks in a specific order, but the specific order of these steps or blocks does not limit the invention described in the claims, and each step or block may be implemented in a different order, or In other words, it is possible to be performed simultaneously with other steps or blocks. In addition, it will be apparent to those skilled in the art that the steps or blocks have not been described in detail, and that at least one other step may be added or deleted without departing from the scope of the invention.

The above-described embodiments include various examples. Those skilled in the art will appreciate that not all possible combinations of examples of the inventions can be described, and that various combinations can be derived from the description herein. Therefore, the protection scope of the invention should be judged by combining various examples described in the detailed description within the scope of the claims described below.

Claims (15)

1. In the method for the base station to perform a V2X (vehicle to everything) communication in a wireless communication system,

   Receiving a V2X bearer indicator indicating a V2X bearer, wherein the V2X bearer is a bearer used for a V2X service;

   Determining that the base station supports only the PC5 based V2X service among the PC5 based V2X service or the Uu based V2X service;

   Withholding resource allocation for the V2X bearer; And

   Transmitting information indicating that resource allocation for the V2X bearer is suspended to a mobility management entity (MME).
2. The method of claim 1,

   If the base station is determined to support only the PC5 based V2X service, resource allocation for the V2X bearer is suspended.
3. The method of claim 1,

   And transmitting information indicating that resource allocation to the V2X bearer is suspended to the terminal.
4. The method of claim 3, wherein

   The base station is a target base station, characterized in that the information transmitted to the terminal is transmitted to the terminal via a source base station.
5. The method of claim 4, wherein

   And the information includes an identifier (ID) of the V2X bearer.
6. The method of claim 1,

   Determining by the base station to support the Uu based V2X service; And

   Allocating resources for the V2X bearer.
7. The method of claim 6,

   Establishing a DRB for the V2X service based on resources allocated for the V2X bearer; And

   Transmitting information indicating that a DRB for the V2X bearer has been established to the MME.
8. In the method for the device to perform a V2X (vehicle to everything) communication in a wireless communication system,

   Receiving from the base station information indicating that resource allocation for a V2X bearer is suspended, wherein the V2X bearer is a bearer used for a V2X service;

   Performing marking on the V2X bearer instructing to suspend deactivation of the V2X bearer; And

   Maintaining the context of the marked V2X bearer.
9. The method of claim 8,

   And if the base station supports only the PC5 based V2X service among the PC5 based V2X service or the Uu based V2X service, resource allocation for the V2X bearer is reserved by the base station.
10. The method of claim 8,

    And the device is a mobility management entity (MME).
11. The method of claim 10,

    Receiving information from the base station indicating that a DRB for the V2X bearer has been established; And

    If the information indicating that the DRB has been established is received, removing the marking from the V2X bearer.
12. The method of claim 8,

    And the device is a terminal.
13. The method of claim 12,

    Receiving an RRC connection reconfiguration message from the base station; And

    If the RRC connection reset message is received, removing the marking on the V2X bearer.
14. The method of claim 13,

    The AS layer of the terminal informs the NAS of the terminal that the DRB for the V2X bearer is established.
15. In the base station performing V2X (vehicle to everything) communication in a wireless communication system,

    Memory; Transceiver; And a processor connecting the memory and the transceiver, wherein the processor

    Control the transceiver to receive a V2X bearer indicator indicating a V2X bearer, wherein the V2X bearer is a bearer used for a V2X service,

    It is determined that the base station supports only the PC5-based V2X service among the PC5-based V2X service or the Uu-based V2X service,

    Suspend resource allocation for the V2X bearer, and

    And the transceiver is configured to control transmitting information to a mobility management entity (MME) indicating that resource allocation for the V2X bearer is suspended.

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